A pretrip routine for testing a refrigeration system described in U.S. Pat. No. 5,172,561 operates by controlling system components first according to a cooling mode scheme, and then according to a heating/defrost mode scheme. During each of the simulated cooling and heat/defrost modes, a control unit monitors an air-aide temperature differential of a refrigeration system evaporator. If the evaporator air side temperature differential is within a range of temperature differentials indicative of the refrigeration system operating properly in each of the simulated cooling and heating/defrost modes, then the refrigeration system is determined to be operational.
The approach described in U.S. Pat. No. 5,172,561 suffers from two major limitations. The first limitation is that the approach is susceptible to false failures. Under certain operating conditions, the evaporator temperature differential will be outside of a range of temperature differential indicative of proper operation in spite of the system being fully operational. Evaporator temperature is likely to be outside of a range indicative of proper operation particularly under extremely humid work space conditions.
The second major limitation of the approach described in U.S. Pat. No. 5,172,561 is that the approach cannot isolate problems within particular refrigeration system components. When a refrigeration system failure is indicated, the system provides only a general alarm that problem exists somewhere in the system, and cannot identify which particular components in the system have failed. Fixing problems pursuant to a general alarm may require inspection of each of several system components.
There is a need for a refrigeration system pretrip routine which is not susceptible to false failures and which can isolate particular problems within a refrigeration system.